Beyond the spontaneous scalarization: New fully nonlinear dynamical mechanism for formation of scalarized black holes

Understand

In the present letter we show the existence of a fully nonlinear dynamical mechanism for the formation of scalarized black holes which is different from the spontaneous scalarization.

• We consider a class of scalar-Gauss-Bonnet gravity theories within which no tachyonic instability can occur.
• Although the Schwarzschild black holes are linearly stable against scalar perturbations, we show dynamically that for certain choices of the coupling function they are unstable against nonlinear scalar perturbations.
• This nonlinear instability leads to the formation of new black holes with scalar hair.